Digital recording discs, including compact discs (CDs), laser discs, and the like, are widely used to store different types of information. Modern digital discs may be formatted for use with audio, video, or computer equipment that reads the data recorded on the discs. The technology associated with digital discs and digital playback equipment is well known to those skilled in the art. Basically, digital information is encoded within a disc beneath an optically transparent protective layer of plastic. A laser beam reads the digital information during playback, and the information is then processed and presented to the user in the form of sound, visual images, or computer data.
If the protective coating is dirty or damaged, then the laser beam may erroneously track or misread the encoded data. Although modern playback devices include error correction techniques, some scratches or pits on the protective coating of a disc may still cause problems during playback. If such imperfections cause the playback device to consistently malfunction, then the disc itself may be unusable. Due to the high cost of digital discs, it is desirable to repair such damaged discs rather than replace them.
In recent years, the CD reclamation industry has prospered due to the widespread use and longevity of compact discs. However, many used CDs cannot be resold because scratches on the protective coating make them unplayable or visually unappealing. A visually acceptable CD typically has a lustrous metallic appearance, desirably having a surface that is sufficiently smooth to accommodate specular reflections. In many cases, even though a CD is audibly or otherwise satisfactory from a performance perspective, a customer will not purchase it if it contains any visual imperfections. Consequently, to improve CD playability and visual appeal, various methods for treating the surface of a CD have been developed. However, these prior art methods suffer from several disadvantages.
One known method for repairing scratches on a digital disc involves applying a wax or other compound to the damaged surface. The wax fills in the pits or scratches in the protective coating, and partially restores the optical clarity of the disc so that the laser can read the data substantially without error. While this process may restore the playing quality of some discs, the discs often remain aesthetically imperfect because the wax does not actually remove the scratches. As such, there is a need for a reconditioning process that improves the readability and visual appearance of a digital disc.
Another known method for reconditioning digital discs requires sanding or grinding the protective coating until the imperfections are no longer present. Typically, this process involves several sequential, time consuming steps using grinding elements or polishing compounds having varying grades. While this method may effectively repair the protective coating of a single digital disc, it is so time consuming that it is impractical for repairing a large number of discs. Thus, there is also a need for a time-efficient method of repairing digital discs.
Another process for repairing damaged digital discs involves the localized removal of scratches or imperfections from the protective layer of the disc. This process may have limited use because the spot removal of imperfections inherently creates an unbalanced disc. An unbalanced CD (which can spin at rotational speeds of up to 500 RPM) may cause focusing problems, vibrations, and signal distortion during playback. Thus, it is desirable to have a method of repairing a digital disc that does not result in an unbalanced disc.
One prior art method for repairing a disc that does not result in an unbalanced disc employs an apparatus that uniformly smoothes the entire surface of the disc. The apparatus includes a buffing wheel which is rotated on an axis perpendicular to the axis of a rotating laser disc. The buffing wheel is under significant compression against the disc to remove scratches or marks on the entire surface of the disc while cleaning the disc. The disc is secured in the apparatus over a latch pin and the central area of the disc is supported on an annular shoulder of a hub. The outer edge of the disc engages and rests on the beveled surface of a driving wheel, and the driving wheel is coupled to the buffing wheel such that when the buffing wheel is hand cranked, the disc rotates. Unfortunately, the hand cranked buffing wheel does not rotate at fast enough speeds to effectively and efficiently buff the disc. Furthermore, faster rotational speeds can not be effectively employed when driving the disc by the outer edge. Moreover, the significant compression of the buffing wheel causes uneven buffing throughout the radial dimension of the disc.